The vacuum pump V22 provides vacuum for the clutch system ONLY, and is operated whenever there is insufficient vacuum in the clutch system (recognized by the opening of the clutch system pressure switch F210).

If this pump is recognized as failed, the priority switching valve is opened and the vacuum for the clutch circuit is provided by the mechanical exhauster, the engine is no longer switched off, green engine running control lamp is lit.

This pump should rarely operate when in motion, and extremely rarely when the engine is running , as the vacuum should be provided by the mechanical exhauster on the diesel engine and should be shared with the brake circuit. If whilst driving a relay appears to be ticking, especially after changing gear, it is likely you have vacuum pressure problems and it would be advisable to check that the vacuum system is leak-free and that the vacuum switches are in good working order.